Purple Rice Extract and Anthocyanidins of the Constituents Protect against Light-Induced Retinal Damage in Vitro and in Vivo

This study evaluated the protective effects of purple rice (Oryza sativa L.) bran extract (PRE) and its major anthocyanidins (cyanidin and peonidin) against light-induced retinal damage. In an in vitro experiment, cultured murine photoreceptor cells (661W) were damaged by a 24 h exposure to light. Viability of 661W after light treatment, assessed by the tetrazolium salt (WST-8) assay and Hoechst 33342 nuclear staining, was improved by the addition of PRE, cyanidin, and peonidin. Intracellular radical activation in 661W, evaluated using the reactive oxygen species (ROS) sensitive probe 5-(and 6)-chloromethyl-2,7-dichlorodihydrofluorescein diacetate acetyl ester (CM-H(2)DCFDA), was reduced by PRE and its anthocyanidins. Electron spin resonance (ESR) measurements showed that PRE, peonidin, and cyanidin all exhibited radical scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide anion radical (O-center dot(2)-), and hydroxyl radical ((OH)-O-center dot). In an in vivo mouse experiment, intravitreous injection of PRE significantly suppressed photoreceptor degeneration induced by exposure to light as revealed by histological analysis using hematoxylin eosin staining. These findings suggest that PRE and its anthocyanidins possess protective effects with antioxidation mechanism in both in vitro and in vivo models of retinal diseases.